Cathedral vs Ls3 test
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Joined: Aug 2009
Posts: 1,845
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From: Coast of San Mateo County Between Pacifica & HMB
Both comparisons in this thread were seriously flawed IMO as mentioned the first test
with significant volume disparities & "mysterious cam Specs , the second
(as mentioned by Tusky) with severely compromised cam Specs for the Cathedral
heads (AFR 230s).
i would suggest as mentioned, starting with Heads from the same manufacturer
(AFR 245 VS 260), (TFS 245 VS 255), (Mast 245 VS 255, or LS1 295 VS LS3 295) or (TSP 245 VS 255) on a
(4.155 X 4.00) 434" 11:0-12.5:1 Comp, Either Holley Hi-Ram or Edelbrock Pro-Flow Intakes
(Runner Lengths & Plenum Volumes need to be equal. LLSR for 7500 RPM,
add 4-6* Intake Duration for the Cathedrals, and add 4-6* Exhaust Duration for
the LS3 Heads something like 250/256-258 Cathedrals VS 246/256-260.
LSA,.... My Bad, Valve Events, specced by Darth or SpeedTigger.
***Mast 295s same specs!***
Compare 3500-7500 as well as 4500-6500 & 5500-7500.
That would be a valid test IMO.
with significant volume disparities & "mysterious cam Specs , the second
(as mentioned by Tusky) with severely compromised cam Specs for the Cathedral
heads (AFR 230s).
i would suggest as mentioned, starting with Heads from the same manufacturer
(AFR 245 VS 260), (TFS 245 VS 255), (Mast 245 VS 255, or LS1 295 VS LS3 295) or (TSP 245 VS 255) on a
(4.155 X 4.00) 434" 11:0-12.5:1 Comp, Either Holley Hi-Ram or Edelbrock Pro-Flow Intakes
(Runner Lengths & Plenum Volumes need to be equal. LLSR for 7500 RPM,
add 4-6* Intake Duration for the Cathedrals, and add 4-6* Exhaust Duration for
the LS3 Heads something like 250/256-258 Cathedrals VS 246/256-260.
LSA,.... My Bad, Valve Events, specced by Darth or SpeedTigger.
***Mast 295s same specs!***
Compare 3500-7500 as well as 4500-6500 & 5500-7500.
That would be a valid test IMO.
To be a valid test it should be the norm and relatable and an LLSR isnt there yet. Those cam specs are also pretty large as well even for larger cid and big runner. Id take a few steps back if it were me.
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Joined: Feb 2018
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From: Lawrenceburg Ky
Hey fellas, i made a really small change on the junkyard dog that paid big dividends at the drag strip today. She pulled 1.36 sixty, 6.54 1/8 mile, and 10.33 quarter mile! Not bad for a small bore stroker with 821 heads 
TECH Senior Member
Joined: Jun 2016
Posts: 22,298
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From: Central Cal.
So what was the small change? WE. MUST. KNOW. lol
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Joined: Feb 2018
Posts: 426
Likes: 293
From: Lawrenceburg Ky
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Staging Lane
Joined: Mar 2018
Posts: 53
Likes: 4
I knew that question was coming. LMAO
My 2 is that I dont really care about what torque or power happens at 3000rpms. 7000 is where the LS3 fun is at. Ive spun it to 7100 and gets there easily and wants more but i don't feel it pulling much so i upshift.
What Hammer said about the intake manifold restricting the LS3 is spot on. He told me that before i got the heads and cam on my LS3 earlier this year ("you'll be disappointed with those heads with the stock manifold"). So ill be posting a stock LS3 manifold in the classifieds soon as soon as i choose/buy the right one.
With that said, its no surprise the BR3 heads won. If you complete the setup (102MM TB and good intake manifold), it becomes even clearer that the rectangular ports are the better heads especially if you have the cubic inch.
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From: Mississippi
TECH Senior Member
Joined: Jun 2016
Posts: 22,298
Likes: 3,619
From: Central Cal.
I remember a Holley carb wouldn't flow its best unless it had either an air cleaner bottom on it or something like it to "straighten" the airflow. Makes sense about the velocity stack. Hilborn injectors were the same way. The old funny cars had stacks about a foot tall on them. It wasn't just for looks... lol
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Joined: Feb 2018
Posts: 426
Likes: 293
From: Lawrenceburg Ky
